Ontario has the biggest measles outbreak in North America with, as of Tuesday, 1,383 confirmed or probable cases in the province and about three-quarters of those involved patients 17 and under.Mary Conlon/The Canadian Press
It is supposed to be an article of faith in Canada that parents and public health officials will shield children from deadly infectious diseases. The outbreaks of measles in Ontario and Alberta suggest this faith is misplaced.
Measles has rocketed back in 2025, with infants, toddlers and adolescents the hardest hit.
As of Tuesday, there were 1,383 confirmed or probable cases in Ontario, according to the province’s chief medical officer of health; about three-quarters of those involved patients 17 and under. In Alberta, the government has recorded 265 cases, 83 per cent of which involve patients 17 and under.
The Ontario and Alberta numbers – and they don’t include the 40 or more cases recorded in Quebec so far in 2025 – are outpacing anything seen in the United States this year.
As of May 1, there were 935 confirmed cases in the U.S. in 2025, according to the Centers for Disease Control and Prevention.
Ontario alone has the biggest measles outbreak in North America. On a per-capita basis compared to the U.S., Ontario‘s outbreak is 21 times bigger.
And yet provincial officials are fighting what is at best a rearguard action, and are not doing what needs to be done to protect children right now.
The problem is that too many children are now vulnerable to measles because they aren’t vaccinated against it.
Of the 84 people with measles in Ontario this year who have required hospitalization (63 of them were children), 80 were not vaccinated.
In Alberta, 138 out of 155 confirmed cases as of April 26 involved unimmunized people.
This is happening even though a perfectly safe and highly effective vaccine has existed for decades. The measles, mumps and rubella (MMR) shot is the reason Canada was able to say in 1998 that measles had been eradicated.
But measles is so contagious – way more so that COVID-19, in fact – that vaccination rates need to be 95 per cent or higher to prevent regression. The virus can spread so easily in the air that an infected person can leave a room (think of a classroom) and the next person who enters can catch the bug.
Which means it doesn’t take much of a drop in vaccination rates for the disease to show itself again.
Measles can also be very dangerous. The CDC says there have been three deaths from measles in the U.S. this year. In Alberta this week, three people were in intensive care. Severe complications such as respiratory failure and encephalitis occur in approximately 1 of every 1,000 reported cases.
But Alberta, Ontario and other provinces failed to react in a timely way to a steady decrease in measles vaccination rates, and to the steady rise in what public health officials like to call “vaccine hesitancy” – but which amounts to an anti-vaccination trend that has brought us to where we are today.
A study from October, 2024, found that the percentage of Canadian children getting their first dose of the MMR vaccine (two doses are required) fell to 82.5 per cent from 89.5 per cent in five provinces from 2019 through 2023.
An earlier study, from 2022, found that the measles vaccination rate in Canada was 90 per cent, well below the 95 per cent needed to sustain measles elimination.
This has now come back to haunt Canada. Instead of taking action when it was apparent that vaccination rates were falling, Ontario and Alberta health officials are stuck with desperately pleading with parents to protect their children – and other people’s children – by getting them vaccinated.
Pleading isn’t good enough. What is needed instead is for the provinces to keep unvaccinated from attending school in person until the outbreak recedes in affected areas.
And then, after that, the provinces need to change policies that allow parents to send unvaccinated children to school. Most provinces don’t require students to be vaccinated to attend class in person. In the two provinces that putatively do – Ontario and New Brunswick – a parent can get an exemption for medical, religious or “philosophical” reasons.
Appeals to reason or to a sense of moral obligation can clearly no longer keep children safe – not in an age where too many parents are refusing to vaccinate their children based on scientifically debunked misinformation, or as a misguided political statement, or out of confusion.
Children cannot protect themselves from contagious diseases; they are entirely dependent on adults for that. And right now, adults are letting them down.